Cut-processing of a metal material is generally conducted in such a manner that a cutting tool holder on which a cutting tool is mounted is installed on a head of a machine tool, rotation of a motor on the head side is transmitted to the cutting tool holder, and the rotating cutting tool is applied to a metal workpiece to be processed while cutting oil is poured on the workpiece. However, in the case where the workpiece has a complicated shape, it is often the case that the cutting oil can not be fully supplied for the reason that the sections to be cut are secluded and the like. When supply of the cutting oil is not sufficient, the temperature of the cutting sections rises suddenly due to the heat caused by friction. As a result, problems such as the processing accuracy deteriorates and the life of the cutting tool is shortened occur.
For example, a valve seat made of a sintered material is embedded in a valve mounting section of a cylinder head of a motor vehicle to secure the airtightness of the valve. Surface processing of this valve seat is currently conducted by a cutting tool attached to a multi-spindle head. However, since the processing surface of the valve seat is situated on the inner side of the cylinder head, when the cutting tool is inserted therein, only a few millimeters of space is left between the workpiece and the cutting tool and as a result, the cutting oil can not be supplied to the processing section. Accordingly, it is also the case that the cutting oil is supplied from the workpiece side, that is, from a guide orifice within the cylinder. However, it is often the case that reaming of the guide orifice is conducted at the same time to increase the working efficiency. In this case, since the guide orifice is closed up by a reaming tool, it is also difficult to adopt this method. In this manner, it is necessary to provide piping for the cutting oil inside a cutting tool holder.
As an example of a technique whereby piping for the cutting oil is provided inside the cutting tool holder, Japanese Patent Application Publication No. 8-39387 discloses a structure wherein the cutting oil supplied through a cutting oil supply orifice provided to penetrate a cutter body is supplied to a cutting face through a cutting oil supply groove provided on a throwaway chip.
Further, in Japanese Patent Application Publication No. 8-57742, a nozzle device is described, in which a plurality of nozzle units adapted to communicate with a cutting oil supply source is swingably disposed on the outer periphery of a main axis of a machine tool or at the tip of a robot arm, the direction of each nozzle is swung all together by a separately provided driving source, and cutting oil is supplied from the cutting oil supply source.
Japanese Patent Application Publication No. 2001-87906 describes a cutting tool which includes a plurality of nozzles to which high pressure cooling fluid is supplied via a conduit system provided inside the cutting tool, wherein a first nozzle and a second nozzle collaborate in pairs to collide with each other above chips a short distance away from a cutting insert, thereby partializing the chips upwards and backwards.
Further, described in Japanese Patent Application Publication No. 2003-1525 is a structure of an oil feeding system whereby the cutting oil is injected from a skimmer nut provided at the end through the inside of a tool holder by making use of the cutting oil of a spindle inside oil feeding system of a machining center, wherein rotation is imparted to the cutting oil to increase the cooling efficiency of a cutting edge.
Techniques described in Japanese Patent Application Publication Nos.: 8-39387, 8-57742, and 2003-1545 cannot be applied to processing of, for example, an engine part of a complicated shape in a remote (secluded) position without space. Further, as shown in the technique of Japanese Patent Application Publication No. 2001-87906, in the case where a cutting fluid supply route penetrates the center of a main axis of a machining center, there is a problem that cut chips get into the cutting fluid supply route and then flow back to cause malfunction of a bearing section of the rotational axis.